Wheezing and gasping chicken. PLEASE HELP!

My 3-year-old Plymouth Rock hen is wheezing and gasping for air. I looked down her throat and there are no abnormalities or blockages. I looked at the opening of her trachea and there seemed to be a small tear, but it wasn't bleeding or discolored. We do have a rooster, and I'm suspicious that he might of broken one of her ribs while mating and it punctured her lung. It started today, I'm sure, because last night she was completely normal. She didn't want to roost in the coop. There is a little blood on the back of her head.
Does anyone know what's wrong?